Question about WD Red Plus

Hard disk works with the DS212j. Hotswap and the like depends very much on how the NAS is currently set up. If the hard drives are currently mirrored, it should work to replace one hard drive, wait until mirroring is restored and then play the game with the second hard drive. Restoring mirroring is super slow though. Backing up data and configuration and then restoring them would be faster. Good luck!